1) Field of the Invention
The present invention relates to an optical module having an electric circuit board to which a photoelectric element is electrically connected, and more particularly, to an optical module used for a data transfer system in a server system and the like.
2) Description of the Related Art
Recently, in data transfer systems such as a server system, data transfer is carried out using an optical signal, while performing data processing using an electric signal, and a so-called optical module is used for the data transfer by the optical signal. The optical module includes a photoelectric transducer (photoelectric element) that converts an electric signal to an optical signal (E/O conversion) or converts an optical signal to an electric signal (O/E conversion), and an optical element that propagates the optical signal therethrough, such as an optical fiber, and is formed by optically coupling these elements. By appropriately combining the photoelectric transducers and the optical elements, an optical transmission module that transmits an optical signal via the optical element and a so-called optical reception module that receives an optical signal via the optical element can be configured.
For example, in the current large-scale server system or the like, a plurality of optical modules are mounted in parallel on an optical module-mounting portion, in order to realize parallel transmission of a large number of optical signals. Therefore, it is desired that the optical modules for parallel transmission used in such a large-scale server system or the like are small and can be manufactured at a low cost, and can realize low power consumption. In order to realize this, for example, the number of parts constituting the optical module is reduced as much as possible, or highly efficient and stabilized optical coupling is realized in the transfer of optical signals in the optical module.
FIG. 20 is an exploded perspective view of a conventional optical module. An optical module 900 shown in FIG. 20 has the primary objective of reduction in cost, among the demands for miniaturization, low cost, and low power consumption. The optical module 900 includes a ferrule 902 housing an optical fiber array 901, an electric circuit board 904 having an electric circuit 903 mounted thereon, a photoelectric transducer 905, a flexible circuit board 906 for electrically connecting the photoelectric transducer 905 to the electric circuit board 904, a support member 908 that supports a micro lens array 907, and a spacer 909 mechanically coupled to the support member 908. In the optical module 900, a facet 902a of the ferrule 902 and the photoelectric transducer 905 are arranged to face each other, the electric circuit board 904 is arranged on the opposite side of the photoelectric transducer 905 facing the ferrule 902, and the photoelectric transducer 905 and the electric circuit board 904 are connected by the flexible circuit board 906 substantially bent at a right angle. Thus, by forming the spacer 909 directly on the flexible circuit board 906, low production cost is realized (see, for example, Japanese Patent Application Laid-Open No. 2000-82830). Other known techniques related to the present invention are disclosed in, for example, Japanese Patent Application Laid-Open Nos. H09-270747, H10-300987, H11-202166, and 2002-98842.
However, in the optical module 900 shown in FIG. 20, since an optical coupling unit (for example, the ferrule 902), which becomes the main mounting portion to the optical module-mounting portion in the server system or the like, and the electric circuit board 904 having the electric circuit 903 are arranged in parallel in a direction of L in FIG. 20, the mounting space of the optical module 900 increases, it is difficult to realize high-density parallel mounting to a module rack or the like due to miniaturization of the optical module-mounting portion, and the server system may become large, thereby restricting realization of the miniaturization and low cost by reduction of the mounting space and the mounting cost.
In order to realize highly efficient optical coupling, parts such as the micro lens array 907, the support member 908, and the spacer 909 are required other than the photoelectric transducer 905 and the ferrule 902, and hence, it is difficult to realize miniaturization and low cost by reducing the number of parts.
The techniques described in Japanese Patent Application Laid-Open Nos. H09-270747, H10-300987, H11-202166, and 2002-98842 do not particularly realize miniaturization, low cost, and low power consumption by reducing the mounting space of the optical module.